HELP WITH WINDOWS MOVIE MAKER?

So, I want to save a video from youtube and use some of the things in it, in a video that I’M making. I FINALLY figured out how to save it but when I want to import it this comes up:
The file C:\Users\Marleigh and Maddie\Downloads\Justin Bieber - Teach Me How To Dougie_ Jerk.3gp cannot be imported because the codec required to play the file is not installed on your computer. If you have already tried to download and install the codec, close and restart Windows Movie Maker, and then try to import the file again.
So, I tried downloading a few codecs, but it STILL isn’t working. I also tried restarting it like the pop-up said, but it didn’t work EITHER! I’m starting to get a little Pissed off (am I aloud to say that on here?) but I REALLY REALLY REALLY need to make the video! I have WMM 2007 if that helps any. What codec should I download? If you could also post a link to a website where you can download it, that would be good too! THANKS!